1. Field of the Invention
The present invention relates to an adaptive differential pulse code modulation system in which both voice signals and MODEM signals more than 9600 bit/sec can be coded.
2. Description of the Related Arts
To maximize efficient use of a public line, a frequency band of a transmission is compressed by using an ADPCM (Adaptive Differential Pulse Code Modulation) system, and in addition, voice signals and MODEM signals are transmitted by using this public line.
Therefore, conventionally, in a CCITT Counsel G21, it is prescribed that a MODEM signal having a transmission speed of 4800 bit/sec may be coded efficiently.
However, the transmission speed of the MODEM has recently improved, and a speed of more than 9600 bit/sec is used. However, the conventional coder cannot code a MODEM signal of more than 9600 bit/sec.